Method of producing non-oriented magnetic steel heavy plate having high magnetic flux density

ABSTRACT

A method of producing non-oriented magnetic steel heavy plate that has good magnetic properties in a low magnetic field that comprises hot-rolling high-purity steel, adjusting the crystal grain size and dehydrogenation treatment, whereby the a uniform ferrite grain diameter is imparted to the steel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of producing non-orientedmagnetic steel heavy plate having high magnetic flux density, formagnetic cores used under DC magnetizing conditions and for magneticshielding.

2. Description of the Prior Art

With the progress in recent years of elementary particle research andmedical instruments, devices using magnets are being used in largestructures and there is a demand for improved performance in suchstructures. Numerous electrical steel sheets having good magnetic fluxdensity have been provided, especially silicon steel sheet andelectrical mild steel sheet.

However, with respect to their use as structural members, there havebeen problems with the assembly fabrication and strength of suchmaterials, and this has necessitated the use of steel heavy plate. Sofar, such electrical steel heavy plate has been produced using pure ironcomponents, as in JP-A No. 60(1985)-96749, for example.

However, with the increase in the size and performance of the devicesconcerned, there is a strong demand for steel materials with bettermagnetic properties, especially a high magnetic flux density in a lowmagnetic field, for instance 80 A/m. With the known steel materials,high magnetic flux density in a low magnetic field of 80 A/m cannot beobtained stably.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of producingnon-oriented magnetic steel heavy plate having high magnetic fluxdensity in a low magnetic field.

Another object of the present invention is to provide a method ofproducing non-oriented magnetic steel heavy plate having a tensilestrength of 40 kg/mm² or more and a high magnetic flux density in a lowmagnetic field.

Another object of the present invention is to provide a method ofproducing non-oriented magnetic steel heavy plate having a tensilestrength of 40 kg/mm² or more, a high specific resistance and a highmagnetic flux density in a low magnetic field.

Another object of the present invention is to provide a method ofproducing non-oriented magnetic steel heavy plate having a low coerciveforce and a high magnetic flux density in a low magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become moreapparent from a consideration of the following detailed descriptiontaken in conjunction with the accompanying drawings in which:

FIG. 1 is a graph showing the effect of the carbon content on magneticflux density at 80 A/m;

FIG. 2 is a graph showing the effect of cavity defect size anddehydrogenation heat treatment temperature on magnetic flux density at80 A/m;

FIG. 3 is a graph showing the relationship between steel slab heatingtemperature/hot-rolling finishing temperature and ferrite grain number;

FIG. 4 is a graph showing the relationship between cold-rollingreduction ratio and ferrite grain number;

FIG. 5 is a graph showing the relationship between aluminum content andferrite grain number;

FIG. 6 is a graph showing the effect of silicon on tensile strength andspecific resistance;

FIG. 7 is a graph showing the relationship between coercive force andnickel content; and

FIG. 8 is a graph showing the relationship between coercive force andtitanium content.

DETAILED DESCRIPTION OF THE INVENTION

The process of magnetization to raise the magnetic flux density in a lowmagnetic field consists of placing degaussed steel in a magnetic fieldand changing the orientation of the magnetic domains by increasing theintensity of the magnetic field so that domains oriented substantiallyin the direction of the magnetic field become preponderant, encroachingon, and amalgamating with, other domains. That is to say, the domainwalls are moved. When the magnetic field is further intensified and themoving of the domain walls is completed, the magnetic orientation of allthe domains is changed. In this magnetization process, the ease withwhich the domain walls can be moved decides the magnetic flux density ina low magnetic field. That is, to obtain a high magnetic flux density ina low magnetic field, obstacles to the movement of the domain wall mustbe reduced as far as possible.

As means of obtaining a high magnetic flux density in a low magneticfield, the inventors carried out detailed investigations relating tocrystal grain size, the effects of elements that cause internal stressesand cavity defects.

AlN has the effect of refining the size of crystal grains, so grain sizecan be coarsened by reducing the AlN. With reference to the productionmethod, the heating temperature is raised as high as possible to coarsenthe size of the austenite grains, and the finish rolling temperature isalso raised as high as possible to prevent the crystal grain size beingrefined by the rolling process, together with which annealing conditionsfollowing rolling are used selectively.

Carbon has to be reduced to reduce internal stresses. FIG. 1 shows thatas the carbon content is increased, magnetic flux density in a lowmagnetic field of 80 A/m goes down. For the samples, (0.01 Si--0.1Mn--0.01 Al) steel was used.

With respect to the effect of cavity defects, it was found that therewas a large degradation in the magnetic properties when cavity defectsmeasured 100 micrometers or more. It was found that in order toeliminate such harmful cavity defects measuring 100 micrometers or more,a shape ratio A of 0.7 or more is required.

As shown by FIG. 2, the presence of hydrogen in the steel isdeleterious, and it was discovered that the magnetic properties could begreatly improved by the use of dehydrogenation heat treatment.

FIG. 2 shows that by using high shape ratio rolling to reduce the sizeof cavity defects to less than 100 micrometers and reducing hydrogen inthe steel by dehydrogenation heat treatment, magnetic flux density in alow magnetic field could be markedly raised. For the samples, (0.007C--0.01 Si--0.1 Mn) steel was used.

Thus, the present invention comprises the steps of:

preparing a steel slab comprising, by weight, up to 0.01 percent carbon,up to 0.20 percent manganese, up to 0.015 percent phosphorus, up to0.010 percent sulfur, up to 0.05 percent chromium, up to 2.0 percentnickel, up to 0.01 percent molybdenum, up to 0.01 percent copper, up to0.004 percent nitrogen, up to 0.005 percent oxygen and up to 0.0002percent hydrogen, and one or more deoxidizing agents selected from agroup consisting of up to 4.0 percent silicon, up to 0.20 percenttitanium, 0.005 to 0.40 percent aluminum, and up to 0.01 percentcalcium, with the remainder being substantially iron;

heating the slab to a temperature of 1150° to 1350° C.;

carrying out at least one hot-rolling at a shape ratio A of at least 0.7at a finish rolling temperature of at least 900° C.;

applying dehydrogenation heat treatment at between 600° and 750° C. forheavy plate with a gage thickness of 50 mm or more;

annealing at a temperature of 700° to 950° C. or normalizing at atemperature of 910° to 1000° C., as required;

applying annealing at a temperature of 750° to 50° C. or normalizing ata temperature of 910° to 1000° C. for hot-rolled heavy plate having agage thickness that is at least 20 mm but less than 50 mm;

whereby a magnetic flux density of 0.8 tesla or more at a magnetic fieldof 80 A/m is imparted to the steel.

This is provided that: ##EQU1## where A: rolled shape ratio

h₁ : entry-side plate thickness (mm)

h₀ : exit-side plate thickness (mm)

R: radius (mm) of rolling roll

In this invention, preferably the steel is high purity steel comprisedof up to 0.01 percent carbon, up to 0.02 percent silicon, up to 0.20percent manganese, up to 0.015 percent phosphorus, up to 0.010 percentsulfur, up to 0.05 percent chromium, up to 0.01 percent molybdenum, upto 0.01 percent copper, 0.005 to 0.40 percent aluminum, up to 0.004percent nitrogen, up to 0.005 percent oxygen and up to 0.0002 percenthydrogen, with the remainder being substantially iron.

The reasons for the component limitations in the high-purity steelreferred to with respect to the present invention will now be explained.

Carbon increases internal stresses in steel and is the element mostresponsible for degradation of magnetic properties, especially magneticflux density in a low magnetic field, and as such, minimizing the carboncontent helps to prevent a drop in the magnetic flux density in a lowmagnetic field. Also, lowering the carbon content decreases the magneticaging of the steel, and thereby extends the length of time the steelretains its good magnetic properties. Hence, carbon is limited to amaximum of 0.010 percent. As shown in FIG. 1, an even higher magneticflux density can be obtained by reducing the carbon content to 0.005percent or less.

Low silicon and manganese are desirable for achieving high magnetic fluxdensity in a low magnetic field; low manganese is also desirable forreducing MnS inclusions. Therefore up to 0.02 percent is specified asthe limit for silicon and up to 0.20 percent for manganese. To reduceMnS inclusions, a manganese content of no more than 0.10 percent ispreferable.

Phosphorus, sulfur and oxygen produce non-metallic inclusions in thesteel, and the segregation of these elements also obstructs the movementof the magnetic domain walls. As such, the higher the content amounts ofthese elements, the more pronounced the deterioration in the magneticflux density and other magnetic properties. Therefore, an upper limit of0.015 percent has been specified for phosphorus, 0.010 percent forsulfur, and 0.005 percent for oxygen.

Because of the adverse affect chromium, molybdenum and copper have onmagnetic flux density in a low magnetic field, preferably the contentamounts of these elements are kept as low as possible. Another reasonfor minimizing these elements is to reduce the degree of segregation.Accordingly, an upper limit of 0.05 percent has been specified forchromium, 0.01 percent for molybdenum and 0.01 percent for copper.

In its role as a deoxidizing agent, aluminum is an indispensable elementfor achieving internal uniformity in materials such as the plateaccording to the present invention, for which purpose a minimum of 0.005percent is added. As excessive aluminum will give rise to inclusions,degrading the quality of the steel, an upper limit of 0.040 percent isspecified. More preferably, the amount of aluminum should not exceed0.020 percent in order to reduce the AlN which has the effect ofrefining the size of the crystal grains.

Because nitrogen increases internal stresses in the steel and in theform of AlN has the effect of refining the size of the crystal grains,thereby causing a deterioration in magnetic flux density in a lowmagnetic field, an upper limit of 0.004 percent has been specified.

To prevent hydrogen having an adverse effect on magnetic properties andpreventing reductions in cavity defects, an upper limit of 0.0002percent hydrogen has been specified.

The method for producing the steel will now be described. The steel isheated to a temperature of 1150° C. prior to rolling in order to coarsenthe size of the austenite grains and improve the magnetic properties. Anupper limit of 1300° C. is specified to prevent scaling loss and toconserve on energy.

If the finish rolling temperature is below 900° C., the rolling willrefine the size of the crystal grains, adversely affecting the magneticproperties. As such, a temperature of 900° C. or more is specified withthe aim of achieving an increase in the magnetic flux density as aresult of a coarsening of the size of the crystal grains.

Regarding the hot rolling, the solidification process will always giverise to cavity defects, although the size of the defects may vary.Rolling has to be used to eliminate such cavity defects, and as such,hot rolling plays an important role. An effective means is to increasethe amount of deformation per hot rolling, so that the deformationextends to the core of the plate.

Specifically, employing a high shape ratio which includes at least onepass at a shape ratio A of at least 0.7 so that the size of the cavitydefects is no larger than 100 micrometers is conducive to obtainingdesirable magnetic properties. Eliminating cavity defects in the rollingprocess by using this high shape ratio rolling markedly enhancesdehydration efficiency in the subsequent dehydrogenation heat treatment.

The following shape ratio A is defined by the following equation.##EQU2## where A: rolled shape ratio

h₁ : entry-side plate thickness (mm)

h₀ : exit-side plate thickness (mm)

R: radius (mm) of rolling roll

Continuing on from the hot rolling, dehydrogenation heat treatment isemployed on heavy plate with a gage thickness of 50 mm or more tocoarsen the size of the crystal grains and remove internal stresses.Hydrogen does not readily disperse in heavy plate having a thickness of50 mm or more, which causes cavity defects and, together with the effectof the hydrogen itself, degrades magnetic flux density in a low magneticfield.

Because of this, dehydrogenation heat treatment is employed. However, ifthe temperature of the dehydrogenation heat treatment is below 600° C.the dehydrogenation efficiency is poor, while if the temperature exceeds750° C. there is a partial onset of transformation. Therefore, atemperature range of 600° to 750° C. is specified. After various studiesrelating to dehydrogenation time, a time of [0.6(t-50)+6]was found to besuitable (here, t stands for the thickness of the plate).

The steel is annealed to coarsen the size of the crystal grains andremove internal stresses. A temperature below 750° C. will not producecoarsening of the crystal grains, while if the temperature exceeds 950°C., uniformity of the crystal grains in the thickness dimension of theplate cannot be maintained. Therefore an annealing temperature range of750° to 950° C. has been specified.

Normalizing is carried out to adjust the crystal grains in the thicknessdimension of the plate and to remove internal stresses. However, with anAc₃ point temperature of below 910° C. or over 1000° C., uniformity ofthe crystal grains in the thickness dimension of the plate cannot bemaintained, so a range of 910° to 1000° C. has been specified for thenormalizing temperature.

The dehydrogenation heat treatment employed for heavy plates having agage thickness of 50 mm or more can also be used for the annealing ornormalizing. As hydrogen readily disperses in heavy plate that is from20 mm to less than 50 mm thick, such heavy plate only requires annealingor normalizing, not dehydrogenation heat treatment.

As another example of the present invention, rolling conditions can beused to coarsen the size of the crystal grains.

FIG. 3 shows the effect of the heating temperature and finishingtemperature on ferrite grain number. The size of the heated austenitegrains is coarsened by using the highest possible heating temperatureand making the finishing temperature in the ferrite zone at or below theAr₃ point. That is, a high degree of processing stresses are introducedinto the ferrite portion, after which annealing or normalizing is usedto produce abnormal grain growth, coarsening the size of the ferritegrains. More specifically, the size of the austenite grains is coarsenedand the magnetic properties are enhanced by making the pre-rollingtemperature 1200° C. or higher. An upper limit of 1350° C. is specifiedto prevent scaling loss and to conserve on energy.

By finishing the rolling at a temperature at or below the Ar₃ point ofthe ferrite zone, process stresses can be introduced into the ferriteportion and combined with the subsequent annealing or normalizing toobtain abnormal grain growth.

For the present invention, appropriate conditions have been elucidatedwhereby abnormal grain growth is achieved to coarsen the size of theferrite grains by the introduction of cold-rolling processing stressesand the use of the following annealing conditions, which was hithertonot possible.

FIG. 4 shows the relationship between cold-rolling reduction ratio andferrite grain size. A major coarsening of the size of the crystal grainsoccurs with a cold-rolling reduction ratio of between 5 percent and 25percent, with the peak being around 10 percent. Therefore, cold rollingis combined with annealing with the aim of achieving a coarsening of thesize of the ferrite grains through abnormal grain growth. A suitablecold-rolling reduction ratio for this is 5 to 25 percent.

The steel is annealed to coarsen the size of the crystal grains andremove internal stresses. A temperature below 750° C. will not produce acoarsening of the crystal grains, while if the temperature exceeds 950°C., uniformity of the crystal grains in the thickness dimension of theplate cannot be maintained. Therefore an annealing temperature range of750° to 950° C. has been specified.

Other examples whereby the size of the crystal grains is coarsened willnow be described. AlN has the effect of refining the size of crystalgrains, so grain size can be coarsened by reducing the AlN. As shown inFIG. 5, lower aluminum produces an increase in the growth of ferritegrains. Where no aluminum has been added, so there is no more the 0.005percent aluminum, abnormal growth of crystal grains takes place.However, if aluminum is not added, it becomes necessary to add adifferent deoxidizing agent.

Instead of aluminum, the inventors found that silicon, titanium, orcalcium are elements that can be used as deoxidizing agents and do notbring about a reduction of the magnetic flux density in a low magneticfield. The added amounts are: 0.1 to 1.0 percent silicon; 0.005 to 0.03percent titanium; and 0.005 to 0.01 percent calcium. Titanium andcalcium may be added in combination.

In addition, as shown in FIG. 6, using silicon as a deoxidizing agentwhere there is no added aluminum can impart to the steel a high tensilestrength of 40 kg/mm² or more, and a high specific resistance of 35μΩ·cm or more. A range of 1.0 to 4.0 percent is specified as the amountto be added, because over 4.0 percent will cause a reduction in magneticflux density in a low magnetic field.

Nickel is an effective element for reducing coercive force withoutreducing magnetic flux density in a low magnetic field. As shown in FIG.7, at least 0.1 percent nickel is required to reduce the coercive force.A content of more than 2.0 percent nickel produces an increase in thecoercive force and reduces the magnetic flux density in a low magneticfield, therefore a range of 0.1 to 2.0 percent has been specified. Thisrange is also desirable as it enables the strength of the steel to beincreased without reducing its magnetic properties.

When titanium is to be used as a deoxidizing agent where there is noadded aluminum, i.e., the aluminum content is no more than 0.005percent, and for achieving a high tensile strength of 40 kg/mm² or more,as shown in FIG. 8, at least 0.04 percent is required. However, as themagnetic flux density in a low magnetic field will be reduced if thereis more than 0.20 percent titanium, a range of 0.04 to 0.20 percent isspecified.

EXAMPLE 1

Electrical steel heavy plate having the compositions listed in Table 1were produced using the inventive and comparative conditions listed inTable 2. As shown, steels 1 to 10 are inventive steels and steels 11 to29 are comparative steels.

Steels 1 to 5, which were finished to a thickness of 100 mm and hadcoarse, uniform grains, exhibited good magnetic properties. Comparedwith steel 1, steel 2, with lower carbon, steels 3 and 4, with lowermanganese, and steel 5, with lower aluminum, showed better magneticproperties. Steels 6 to 8, which were finished to a thickness of 500 mm,steel 9, which was finished to a thickness of 40 mm, and steel 10, whichwas finished to a thickness of 20 mm, each had coarse, uniform grainsand exhibited good magnetic properties.

As a result of the upper limit being exceeded for carbon in steel 11,manganese in steel 12, phosphorus in steel 13, sulfur in steel 14,chromium in steel 15, molybdenum in steel 16, copper in steel 17,aluminum in steel 18, nitrogen in steel 19, oxygen in steel 20 andhydrogen in steel 21, each of these steels had poorer magneticproperties.

Poorer magnetic properties were also shown by steel 22 because theheating temperature used was too low, by steel 23 because the rollingfinishing temperature was too low, by steel 24 because the maximum shaperatio was too low, by steel 25 because the dehydrogenation temperaturewas too low, by steel 26 because the annealing temperature was too low,by steel 27 because the normalizing temperature was too low and by steel28 because no dehydrogenation was applied.

                                      TABLE 1                                     __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Al N  O  H                                   __________________________________________________________________________    Inven-                                                                              1  0.007                                                                            0.01                                                                             0.15                                                                             0.010                                                                            0.003                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.003                                                                            0.004                                                                            0.00007                             tion  2  0.003                                                                            0.01                                                                             0.14                                                                             0.011                                                                            0.003                                                                            0.03                                                                             0.008                                                                            0.01                                                                             0.035                                                                            0.003                                                                            0.003                                                                            0.00007                                   3  0.007                                                                            0.01                                                                             0.08                                                                             0.009                                                                            0.003                                                                            0.03                                                                             0.010                                                                            0.01                                                                             0.035                                                                            0.003                                                                            0.003                                                                            0.00007                                   4  0.006                                                                            0.01                                                                             0.01                                                                             0.012                                                                            0.002                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.025                                                                            0.003                                                                            0.003                                                                            0.00007                                   5  0.007                                                                            0.01                                                                             0.15                                                                             0.008                                                                            0.008                                                                            0.03                                                                             0.009                                                                            0.01                                                                             0.010                                                                            0.002                                                                            0.004                                                                            0.00006                                   6  0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                   7  0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                   8  0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.004                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                   9  0.006                                                                            0.01                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.032                                                                            0.003                                                                            0.003                                                                            0.00008                                   10 0.007                                                                            0.01                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.025                                                                            0.003                                                                            0.002                                                                            0.00011                             Compara-                                                                            11 0.020                                                                            0.01                                                                             0.16                                                                             0.012                                                                            0.004                                                                            0.05                                                                             0.009                                                                            0.01                                                                             0.030                                                                            0.003                                                                            0.003                                                                            0.00008                             tive  12 0.007                                                                            0.01                                                                             0.30                                                                             0.012                                                                            0.002                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.038                                                                            0.002                                                                            0.002                                                                            0.00006                                   13 0.008                                                                            0.01                                                                             0.15                                                                             0.020                                                                            0.001                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.035                                                                            0.002                                                                            0.003                                                                            0.00005                                   14 0.006                                                                            0.01                                                                             0.14                                                                             0.010                                                                            0.015                                                                            0.03                                                                             0.006                                                                            0.01                                                                             0.035                                                                            0.002                                                                            0.003                                                                            0.00015                                   15 0.007                                                                            0.01                                                                             0.15                                                                             0.010                                                                            0.003                                                                            0.10                                                                             0.005                                                                            0.01                                                                             0.036                                                                            0.002                                                                            0.002                                                                            0.00008                                   16 0.006                                                                            0.01                                                                             0.13                                                                             0.012                                                                            0.003                                                                            0.04                                                                             0.050                                                                            0.01                                                                             0.035                                                                            0.003                                                                            0.002                                                                            0.00007                                   17 0.007                                                                            0.02                                                                             0.13                                                                             0.013                                                                            0.002                                                                            0.04                                                                             0.007                                                                            0.03                                                                             0.020                                                                            0.003                                                                            0.002                                                                            0.00006                                   18 0.009                                                                            0.01                                                                             0.15                                                                             0.013                                                                            0.003                                                                            0.04                                                                             0.006                                                                            0.01                                                                             0.060                                                                            0.003                                                                            0.003                                                                            0.00005                                   19 0.008                                                                            0.01                                                                             0.16                                                                             0.014                                                                            0.002                                                                            0.03                                                                             0.005                                                                            0.01                                                                             0.030                                                                            0.006                                                                            0.003                                                                            0.00004                                   20 0.008                                                                            0.01                                                                             0.13                                                                             0.015                                                                            0.006                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.029                                                                            0.002                                                                            0.010                                                                            0.00005                                   21 0.007                                                                            0.01                                                                             0.12                                                                             0.014                                                                            0.006                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.025                                                                            0.002                                                                            0.003                                                                            0.00030                                   22 0.008                                                                            0.01                                                                             0.16                                                                             0.010                                                                            0.002                                                                            0.02                                                                             0.008                                                                            0.01                                                                             0.025                                                                            0.002                                                                            0.002                                                                            0.00008                                   23 0.007                                                                            0.01                                                                             0.16                                                                             0.008                                                                            0.002                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.030                                                                            0.003                                                                            0.002                                                                            0.00007                                   24 0.006                                                                            0.02                                                                             0.17                                                                             0.002                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.038                                                                            0.003                                                                            0.003                                                                            0.00006                                   25 0.009                                                                            0.01                                                                             0.16                                                                             0.001                                                                            0.008                                                                            0.04                                                                             0.006                                                                            0.01                                                                             0.036                                                                            0.003                                                                            0.003                                                                            0.00005                                   26 0.007                                                                            0.01                                                                             0.16                                                                             0.012                                                                            0.002                                                                            0.03                                                                             0.005                                                                            0.01                                                                             0.025                                                                            0.002                                                                            0.002                                                                            0.00004                                   27 0.008                                                                            0.01                                                                             0.17                                                                             0.012                                                                            0.002                                                                            0.03                                                                             0.004                                                                            0.01                                                                             0.036                                                                            0.003                                                                            0.002                                                                            0.00018                                   28 0.008                                                                            0.01                                                                             0.15                                                                             0.013                                                                            0.002                                                                            0.03                                                                             0.005                                                                            0.01                                                                             0.029                                                                            0.002                                                                            0.003                                                                            0.00008                             __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________                   Finish  Dehydrogenate Normal-    Cavity  Magnetic                        Heating                                                                            Rolling Heat treating                                                                         Annealing                                                                           izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel     Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.   Temp. Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at                                                                           80Λ/m)         No.       (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                        (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              1   1250 940 0.9 700     --    --   100   20  0   0.95                  tion  2   1250 940 0.9 700     --    --   100   25  0   1.25                        3   1250 940 0.9 700     --    --   100   25  0   1.18                        4   1250 940 0.9 700     --    --   100   20  0   1.24                        5   1150 940 0.9 700     --    --   100   25  0   1.15                        6   1250 980 0.8 720     --    --   500   90  -1  0.95                        7   1250 980 0.8 720     850   --   500   90  -1  1.00                        8   1250 980 0.8 720     --    930  500   90  -1  0.97                        9   1250 920 1.1 --      850   --   40    10  0   1.05                        10  1250 910 1.2 --      --    930  20    5   0   1.00                  Compara-                                                                            11  1250 930 0.85                                                                              680     --    --   200   80  0   0.40                  tive  12  1200 930 0.85                                                                              680     --    --   200   80  0   0.70                        13  1250 930 0.85                                                                              680     --    --   200   85  0   0.65                        14  1250 930 0.85                                                                              680     --    --   200   75  3   0.70                        15  1250 930 0.85                                                                              680     --    --   200   80  0   0.71                        16  1250 930 0.85                                                                              680     --    --   200   80  0   0.68                        17  1250 930 0.85                                                                              680     --    --   200   75  0   0.70                        18  1250 930 0.85                                                                              680     --    --   200   80  5   0.55                        19  1250 930 0.85                                                                              680     --    --   200   75  4   0.60                        20  1250 930 0.85                                                                              680     --    --   200   80  0   0.65                        21  1250 930 0.85                                                                              680     --    --   200   95  0   0.65                        22  1050 930 0.85                                                                              680     --    --   200   80  6   0.50                        23  1200 850 0.85                                                                              680     --    --   200   75  5   0.55                        24  1200 930 0.6 680     --    --   200   150 2   0.65                        25  1200 920 0.9 550     --    --   200   80  0   0.60                        26  1200 920 1.1 --      700   --   40    10  0   0.60                        27  1200 920 1.1 --      --    1050 40    10  0   0.65                        28  1200 920 0.9 --      850   --   200   70  0   0.60                  __________________________________________________________________________

EXAMPLE 2

Steels 5 to 10 and steels 22 and 23 of Example 1 were used to produceelectrical steel heavy plates using the heating conditions andhot-rolling finishing temperatures listed in Table 3.

Inventive steels 5 to 10, which each had coarse, uniform grains,exhibited good magnetic properties. Comparative steels 22 and 23 showedinferior magnetic flux densities owing to the heating temperature beingtoo low in the case of the former and the rolling finishing temperaturetoo high in the case of the latter.

                                      TABLE 3                                     __________________________________________________________________________                   Finish  Dehydrogenate Normal-    Cavity  Magnetic                        Heating                                                                            Rolling Heat treating                                                                         Annealing                                                                           izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel     Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.   Temp. Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at                                                                           80Λ/m)         No.       (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                        (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              5   1200 700 0.9 700     --    --   100   25  -1  1.25                  tion  6   1250 710 0.8 720     --    --   500   90  -2  1.05                        7   1250 710 0.8 720     850   --   500   90  -2  1.10                        8   1250 710 0.8 720     --    930  500   90  -2  1.07                        9   1300 690 1.1 --      850   --   40    10  -1  1.15                        10  1300 690 1.2 --      --    930  20     5  -1  1.10                  Compara-                                                                            22  1150 710 0.85                                                                              680     --    --   200   80   5  0.55                  tive  23  1250 850 0.85                                                                              680     --    --   200   75   5  0.55                  __________________________________________________________________________

EXAMPLE 3

Steels 5 to 10 and steels 22 and 23 of Example 1 were used to produceelectrical steel heavy plates using the conditions listed in Table 4.

Inventive steels 5 to 10, which each had coarse, uniform grains,exhibited a high magnetic flux density. Comparative steels 22 and 23showed poor magnetic properties owing to the heating temperature beingtoo low in the case of the former and the rolling finishing temperaturetoo low in the case of the latter.

                                      TABLE 4                                     __________________________________________________________________________                  Finish  Dehydrogenate  Normal-    Cavity  Magnetic                       Heating                                                                            Rolling Heat treating                                                                         Cold Rolling                                                                         izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel    Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.   Reduction                                                                            Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at 80A/m)            No.      (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (%)    (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              5  1150 940 0.9 700     10     850  120   25  -3  1.30                  tion  6  1250 990 0.8 720     10     850  550   90  -3  1.10                        7  1250 980 0.8 720     5      850  550   90  -2  1.00                        8  1250 980 0.8 720     25     850  550   90  -2  0.98                        9  1250 920 1.1 --      15     750  50    10  -2  1.20                        10 1250 910 1.2 --      15     950  20    5   -2  1.15                  Compara-                                                                            22 1050 930 0.85                                                                              680     10     850  250   80   4  0.55                  tive  23 1200 850 0.85                                                                              680     10     850  250   75   3  0.60                  __________________________________________________________________________

EXAMPLE 4

Electrical steel heavy plate having the compositions listed in Table 5were produced using the conditions listed in Table 6.

Inventive steels 29 to 35, which each had coarse, uniform grains,exhibited good magnetic properties.

                                      TABLE 5                                     __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Al N  O  H                                   __________________________________________________________________________    Inven-                                                                              29 0.007                                                                            0.5                                                                              0.16                                                                             0.011                                                                            0.003                                                                            0.03                                                                             0.008                                                                            0.01                                                                             0.003                                                                            0.003                                                                            0.003                                                                            0.00006                             tion  30 0.007                                                                            0.3                                                                              0.15                                                                             0.008                                                                            0.008                                                                            0.03                                                                             0.009                                                                            0.01                                                                             0.001                                                                            0.002                                                                            0.004                                                                            0.00006                                   31 0.008                                                                            0.3                                                                              0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.003                                                                            0.002                                                                            0.004                                                                            0.00006                                   32 0.008                                                                            0.4                                                                              0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.004                                                                            0.002                                                                            0.004                                                                            0.00006                                   33 0.008                                                                            0.3                                                                              0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.003                                                                            0.002                                                                            0.004                                                                            0.00006                                   34 0.006                                                                            0.3                                                                              0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.003                                                                            0.003                                                                            0.003                                                                            0.00008                                   35 0.007                                                                            0.3                                                                              0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.002                                                                            0.003                                                                            0.002                                                                            0.00011                             __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________                  Finish  Dehydrogenate  Normal-    Cavity  Magnetic                       Heating                                                                            Rolling Heat treating                                                                          Annealing                                                                           izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel    Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.    Temp. Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at                                                                           80Λ/m)         No.      (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                           (°C.)                                                                        (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              29 1250 940 0.9 700      --    --   100   25  -3  0.95                  tion  30 1150 940 0.9 700      --    --   100   50  -3  1.25                        31 1250 980 0.8 720      --    --   500   90  -2  1.05                        32 1250 980 0.8 720      850   --   500   90  -2  1.10                        33 1250 980 0.8 720      --    930  500   90  -2  1.07                        34 1250 920 1.1 --       850   --   40    10  -3  1.15                        35 1250 910 1.2 --       --    930  20    5   -3  1.10                  __________________________________________________________________________

EXAMPLE 5

Electrical steel heavy plate having the compositions listed in Table 7were produced using the conditions listed in Table 8.

Inventive steels 36 to 41, which each had coarse, uniform grains,exhibited good magnetic properties.

Comparative steels 42 and 43, each having high aluminum, showed poormagnetic properties.

                                      TABLE 7                                     __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Ti  Al N  O  H                               __________________________________________________________________________    Inven-                                                                              36 0.007                                                                            0.02                                                                             0.15                                                                             0.008                                                                            0.008                                                                            0.03                                                                             0.009                                                                            0.01                                                                             0.001                                                                             0.001                                                                            0.002                                                                            0.004                                                                            0.00006                         tion  37 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.002                                                                             0.003                                                                            0.002                                                                            0.004                                                                            0.00006                               38 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.002                                                                             0.004                                                                            0.002                                                                            0.004                                                                            0.00006                               39 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.002                                                                             0.003                                                                            0.002                                                                            0.004                                                                            0.00006                               40 0.006                                                                            0.01                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.002                                                                             0.003                                                                            0.003                                                                            0.003                                                                            0.00008                               41 0.007                                                                            0.02                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.002                                                                             0.002                                                                            0.003                                                                            0.002                                                                            0.00011                         Compara-                                                                            42 0.009                                                                            0.01                                                                             0.15                                                                             0.013                                                                            0.003                                                                            0.04                                                                             0.006                                                                            0.01                                                                             0.01                                                                              0.010                                                                            0.003                                                                            0.003                                                                            0.00005                         tive  43 0.006                                                                            0.01                                                                             0.12                                                                             0.008                                                                            0.002                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.01                                                                              0.040                                                                            0.003                                                                            0.003                                                                            0.00005                         __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________                   Finish  Dehydrogenate Normal-    Cavity  Magnetic                        Heating                                                                            Rolling Heat treating                                                                         Annealing                                                                           izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel     Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.   Temp. Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at 80A/m)            No.       (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                        (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              36  1150 940 0.9 700     --    --   100   50  -3  1.23                  tion  37  1250 980 0.8 720     --    --   500   90  -2  1.03                        38  1250 980 0.8 720     850   --   500   90  -2  1.08                        39  1250 980 0.8 720     --    930  500   90  -2  1.05                        40  1250 920 1.1 --      850   --   40    10  -3  1.13                        41  1250 910 1.2 --      --    930  20     5  -3  1.08                  Compara-                                                                            42  1250 930 0.95                                                                              680     --    --   200   80   4  0.53                  tive  43  1250 930 0.85                                                                              680     --    --   200   85   5  0.38                  __________________________________________________________________________

EXAMPLE 6

Electrical steel heavy plate having the compositions listed in Table 9were produced using the conditions listed in Table 10.

Inventive steels 44 to 49, which each had coarse, uniform grains,exhibited good magnetic properties.

Comparative steels 42, with high calcium, and 43, with high aluminum,showed poor magnetic properties.

                                      TABLE 9                                     __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Ca Al N  O  H                                __________________________________________________________________________    Inven-                                                                              44 0.007                                                                            0.02                                                                             0.15                                                                             0.008                                                                            0.008                                                                            0.03                                                                             0.009                                                                            0.01                                                                             0.002                                                                            0.001                                                                            0.002                                                                            0.004                                                                            0.00006                          tion  45 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.001                                                                            0.003                                                                            0.002                                                                            0.004                                                                            0.00006                                46 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.003                                                                            0.004                                                                            0.002                                                                            0.004                                                                            0.00006                                47 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.003                                                                            0.003                                                                            0.002                                                                            0.004                                                                            0.00006                                48 0.006                                                                            0.01                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.003                                                                            0.003                                                                            0.003                                                                            0.003                                                                            0.00008                                49 0.007                                                                            0.02                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.001                                                                            0.002                                                                            0.003                                                                            0.002                                                                            0.00011                          Compara-                                                                            50 0.007                                                                            0.01                                                                             0.14                                                                             0.009                                                                            0.06                                                                             0.03                                                                             0.008                                                                            0.01                                                                             0.020                                                                            0.003                                                                            0.003                                                                            0.003                                                                            0.00006                          tive  51 0.006                                                                            0.01                                                                             0.12                                                                             0.008                                                                            0.002                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.001                                                                            0.040                                                                            0.003                                                                            0.003                                                                            0.00005                          __________________________________________________________________________

                                      TABLE 10                                    __________________________________________________________________________                   Finish  Dehydrogenate Normal-    Cavity  Magnetic                        Heating                                                                            Rolling Heat treating                                                                         Annealing                                                                           izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel     Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.   Temp. Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at                                                                           80Λ/m)         No.       (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                        (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              44  1150 940 0.9 700     --    --   100   25  -3  1.22                  tion  45  1250 980 0.8 720     --    --   500   90  -2  1.02                        46  1250 980 0.8 720     850   --   500   90  -2  1.09                        47  1250 980 0.8 720     --    930  500   90  -2  1.04                        48  1250 920 1.1 --      850   --    40   10  -3  1.14                        49  1250 910 1.2 --      --    930   20    5  -3  1.09                  Compara-                                                                            50  1250 930 0.85                                                                              680     --    --   200   85   0  0.45                  tive  51  1250 930 0.85                                                                              680     --    --   200   85    5 0.40                  __________________________________________________________________________

EXAMPLE 7

Electrical steel heavy plate having the compositions listed in Table 11were produced using the conditions listed in Table 12.

Inventive steels 52 to 56, which each had coarse, uniform grains,exhibited good magnetic properties.

Comparative steels 57, which had high titanium, 58, which had highcalcium, 59, which had high titanium and high calcium, and 60, which hadhigh aluminum, each showed poor magnetic properties.

EXAMPLE 8

Electrical steel heavy plate having the compositions listed in Table 13were produced using the conditions listed in Table 14.

Inventive steels 61 to 67, which each had coarse, uniform grains,exhibited a tensile strength of 40 kg/mm² or more, high specificresistance and high magnetic flux density in a low magnetic field.

Comparative steel 68, with low silicon, had low tensile strength andspecific resistance. Comparative steels 69, with high silicon, and 70,with high aluminum, each had a low magnetic flux density.

                                      TABLE 11                                    __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Ti Ca Al N  O  H                             __________________________________________________________________________    Inven-                                                                              52 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.02                                                                             0.002                                                                            0.003                                                                            0.002                                                                            0.004                                                                            0.00006                       tion  53 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.02                                                                             0.003                                                                            0.004                                                                            0.002                                                                            0.004                                                                            0.00006                             54 0.008                                                                            0.01                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.02                                                                             0.002                                                                            0.003                                                                            0.002                                                                            0.004                                                                            0.00006                             55 0.006                                                                            0.01                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.02                                                                             0.001                                                                            0.003                                                                            0.003                                                                            0.003                                                                            0.00008                             56 0.007                                                                            0.02                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.02                                                                             0.001                                                                            0.002                                                                            0.003                                                                            0.002                                                                            0.00011                       Compara-                                                                            57 0.007                                                                            0.01                                                                             0.14                                                                             0.009                                                                            0.003                                                                            0.03                                                                             0.008                                                                            0.01                                                                             0.04                                                                             0.001                                                                            0.003                                                                            0.003                                                                            0.003                                                                            0.00006                       tive  58 0.007                                                                            0.01                                                                             0.13                                                                             0.008                                                                            0.003                                                                            0.03                                                                             0.007                                                                            0.01                                                                             0.02                                                                             0.02                                                                             0.003                                                                            0.003                                                                            0.003                                                                            0.00007                             59 0.008                                                                            0.01                                                                             0.14                                                                             0.008                                                                            0.003                                                                            0.03                                                                             0.007                                                                            0.01                                                                             0.04                                                                             0.02                                                                             0.003                                                                            0.003                                                                            0.003                                                                            0.00007                             60 0.009                                                                            0.01                                                                             0.15                                                                             0.013                                                                            0.003                                                                            0.04                                                                             0.006                                                                            0.01                                                                             0.01                                                                             0.002                                                                            0.010                                                                            0.003                                                                            0.003                                                                            0.00005                       __________________________________________________________________________

                                      TABLE 12                                    __________________________________________________________________________                   Finish  Dehydrogenate Normal-    Cavity  Magnetic                        Heating                                                                            Rolling Heat treating                                                                         Annealing                                                                           izing      Defect                                                                            Ferrite                                                                           Flux Density          Steel     Temp.                                                                              Temp.                                                                             Shape                                                                             Temp.   Temp. Temp.                                                                              Thickness                                                                           Size                                                                              Grain                                                                             (at                                                                           80Λ/m)         No.       (°C.)                                                                       (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                        (°C.)                                                                       (mm)  (μ)                                                                            No. (tesla)               __________________________________________________________________________    Inven-                                                                              52  1250 980 0.8 720     --    --   500   90  -2  1.05                  tion  53  1250 980 0.8 720     850   --   500   90  -2  1.11                        54  1250 980 0.8 720     --    930  500   90  -2  1.08                        55  1250 920 1.1 --      850   --   40    10  -3  1.16                        56  1250 910 1.2 --      --    930  20    5   -3  1.11                  Compara-                                                                            57  1250 930 0.85                                                                              680     --    --   200   85  0   0.42                  tive  58  1250 930 0.85                                                                              680     --    --   200   80  0   0.40                        59  1250 930 0.85                                                                              680     --    --   200   85  0   0.38                        60  1250 930 0.85                                                                              680     --    --   200   80  4   0.55                  __________________________________________________________________________

                                      TABLE 13                                    __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si                                                                              Mn P  S  Cr Mo Cu Al N  O  H                                    __________________________________________________________________________    Inven-                                                                              61 0.007                                                                            3.2                                                                             0.15                                                                             0.008                                                                            0.004                                                                            0.03                                                                             0.009                                                                            0.01                                                                             0.010                                                                            0.002                                                                            0.004                                                                            0.00006                              tion  62 0.007                                                                            3.2                                                                             0.13                                                                             0.009                                                                            0.003                                                                            0.03                                                                             0.008                                                                            0.01                                                                             0.003                                                                            0.002                                                                            0.004                                                                            0.00008                                    63 0.008                                                                            3.0                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                    64 0.008                                                                            2.0                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                    65 0.008                                                                            3.2                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                    66 0.006                                                                            3.8                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.032                                                                            0.003                                                                            0.003                                                                            0.00008                                    67 0.007                                                                            3.6                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.025                                                                            0.003                                                                            0.002                                                                            0.00011                              Compara-                                                                            68 0.006                                                                            0.5                                                                             0.14                                                                             0.010                                                                            0.003                                                                            0.03                                                                             0.006                                                                            0.01                                                                             0.039                                                                            0.003                                                                            0.002                                                                            0.00007                              tive  69 0.007                                                                            4.5                                                                             0.13                                                                             0.009                                                                            0.002                                                                            0.02                                                                             0.007                                                                            0.01                                                                             0.021                                                                            0.002                                                                            0.003                                                                            0.00008                                    70 0.009                                                                            2.0                                                                             0.15                                                                             0.013                                                                            0.003                                                                            0.04                                                                             0.006                                                                            0.01                                                                             0.060                                                                            0.003                                                                            0.003                                                                            0.00005                              __________________________________________________________________________

                                      TABLE 14                                    __________________________________________________________________________                         Dehydro-                                                                      genate                          Magnetic                          Heat-                                                                             Finish  Heat Anneal-                                                                            Normal-  Cavity  Tensil                                                                             Flux  Resis-                      ing Rolling treating                                                                           ing  izing                                                                              Thick-                                                                            Defect                                                                            Ferrite                                                                           Strength                                                                           Density                                                                             tivity             Steel    Temp.                                                                             Temp.                                                                             Shape                                                                             Temp.                                                                              Temp.                                                                              Temp.                                                                              ness                                                                              Size                                                                              Grain                                                                             (kgf/                                                                              (at                                                                                 (μΩ                                                                  ·         No.      (°C.)                                                                      (°C.)                                                                      Ratio                                                                             (°C.)                                                                       (°C.)                                                                       (°C.)                                                                       (mm)                                                                              (μ)                                                                            No. mm.sup.2)                                                                          (tesla                                                                              cm)                __________________________________________________________________________    Inven-                                                                              61 1150                                                                              940 0.9 700  --   --   100 25  -1  46.3 1.15  44.6               tion  62 1150                                                                              940 0.9 700  --   --   100 20  -3  46.5 1.30  44.3                     63 1250                                                                              980 0.8 720  --   --   500 90  -1  46.3 0.95  43.2                     64 1250                                                                              980 0.8 720  850  --   500 90  -1  43.2 1.00  39.8                     65 1250                                                                              980 0.8 720  --   930  500 90  -1  46.2 0.97  44.5                     66 1250                                                                              920 1.1 --   850  --    40 10   0  48.5 1.05  46.1                     67 1250                                                                              910 1.2 --   --   930   20  5   0  48.0 1.00  45.1               Compara-                                                                            68 1250                                                                              930 0.85                                                                              680  --   --   200 85   0  38.0 0.82  33.1               tive  69 1250                                                                              930 0.85                                                                              680  --   --   200 80   0  51.1 0.43  48.4                     70 1250                                                                              930 0.85                                                                              680  --   --   200 80   5  43.2 0.55  39.7               __________________________________________________________________________

EXAMPLE 9

Electrical steel heavy plate having the compositions listed in Table 15were produced using the conditions listed in Table 16.

Inventive steels 71 to 77, which each had coarse, uniform grains,exhibited a high magnetic flux density in a low magnetic field, and alow coercive force.

Comparative steel 78, with low nickel, which did show a high magneticflux density in a low magnetic field, had a high coercive force. Becauseof excessive nickel, comparative steel 79 exhibited a low magnetic fluxdensity in a low magnetic field together with a high coercive force.Comparative steel 80, with high aluminum, showed a low magnetic fluxdensity in a low magnetic field.

                                      TABLE 15                                    __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Ni Al N  O  H                                __________________________________________________________________________    Inven-                                                                              71 0.006                                                                            0.01                                                                             0.01                                                                             0.012                                                                            0.002                                                                            0.04                                                                             0.008                                                                            0.01                                                                             2.0                                                                              0.025                                                                            0.003                                                                            0.003                                                                            0.00007                          tion  72 0.007                                                                            0.01                                                                             0.15                                                                             0.008                                                                            0.008                                                                            0.03                                                                             0.009                                                                            0.01                                                                             1.0                                                                              0.010                                                                            0.002                                                                            0.004                                                                            0.00006                                73 0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.9                                                                              0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                74 0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             1.0                                                                              0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                75 0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             1.0                                                                              0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                76 0.006                                                                            0.01                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             1.0                                                                              0.032                                                                            0.003                                                                            0.003                                                                            0.00008                                77 0.007                                                                            0.01                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             1.0                                                                              0.025                                                                            0.003                                                                            0.002                                                                            0.00011                          Compara-                                                                            78 0.007                                                                            0.01                                                                             0.14                                                                             0.012                                                                            0.002                                                                            0.03                                                                             0.007                                                                            0.01                                                                              0.05                                                                            0.025                                                                            0.002                                                                            0.003                                                                            0.00009                          tive  79 0.007                                                                            0.01                                                                             0.13                                                                             0.010                                                                            0.002                                                                            0.03                                                                             0.006                                                                            0.01                                                                             2.5                                                                              0.023                                                                            0.002                                                                            0.003                                                                            0.00008                                80 0.009                                                                            0.01                                                                             0.15                                                                             0.013                                                                            0.003                                                                            0.04                                                                             0.006                                                                            0.01                                                                             1.0                                                                              0.060                                                                            0.003                                                                            0.003                                                                            0.00005                          __________________________________________________________________________

                                      TABLE 16                                    __________________________________________________________________________             Heat-                                                                             Finish  Dehydrogenate                                                                         Anneal-                                                                            Normal-  Cavity  Magnetic                            ing Rolling Heat treating                                                                         ing  izing                                                                              Thick-                                                                            Defect                                                                            Ferrite                                                                           Flux                                                                                 Coercive            Steel    Temp.                                                                             Temp.                                                                             Shape                                                                             Temp.   Temp.                                                                              Temp.                                                                              ness                                                                              Size                                                                              Grain                                                                             (at 80Λ/m)                                                                    Force               No.      (°C.)                                                                      (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                       (°C.)                                                                       (mm)                                                                              (μ)                                                                            No. (tesla)                                                                              (A/m)               __________________________________________________________________________    Inven-                                                                              71 1250                                                                              940 0.9 700     --   --   100 20  0   1.22   59                  tion  72 1150                                                                              940 0.9 700     --   --   100 25  -1  1.13   55                        73 1250                                                                              980 0.8 720     --   --   500 90  -1  0.93   56                        74 1250                                                                              980 0.8 720     850  --   500 90  -1  0.98   55                        75 1250                                                                              980 0.8 720     --   930  500 90  -1  0.95   55                        76 1250                                                                              920 1.1 --      850  --    40 10  0   1.03   55                        77 1250                                                                              910 1.2 --      --   930   20  5  0   0.98   55                  Compara-                                                                            78 1250                                                                              930  0.85                                                                             680     --   --   200 80  0   0.84   71                  tive  79 1250                                                                              930  0.85                                                                             680     --   --   200 75  0   0.55   70                        80 1250                                                                              930  0.85                                                                             680     --   --   200 80  5   0.53   53                  __________________________________________________________________________

EXAMPLE 10

Electrical steel heavy plate having the compositions listed in Table 17were produced using the conditions listed in Table 18.

Inventive steels 81 to 87, which each had coarse, uniform grains,exhibited good tensile strength and magnetic properties.

Comparative steel 88 showed low tensile strength owing to a titaniumcontent that was too low. Comparative steels 89, with high titanium, 90,with high aluminum, each showed poor magnetic properties.

                                      TABLE 17                                    __________________________________________________________________________    Steel    (wt %)                                                               No.      C  Si Mn P  S  Cr Mo Cu Ti Al N  O  H                                __________________________________________________________________________    Inven-                                                                              81 0.007                                                                            0.01                                                                             0.15                                                                             0.008                                                                            0.004                                                                            0.03                                                                             0.009                                                                            0.01                                                                             0.10                                                                             0.010                                                                            0.002                                                                            0.004                                                                            0.00006                          tion  82 0.007                                                                            0.01                                                                             0.13                                                                             0.005                                                                            0.003                                                                            0.03                                                                             0.008                                                                            0.01                                                                             0.10                                                                             0.002                                                                            0.003                                                                            0.004                                                                            0.00007                                83 0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.12                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                84 0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.13                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                85 0.008                                                                            0.02                                                                             0.14                                                                             0.005                                                                            0.008                                                                            0.04                                                                             0.007                                                                            0.01                                                                             0.08                                                                             0.030                                                                            0.002                                                                            0.004                                                                            0.00006                                86 0.006                                                                            0.01                                                                             0.17                                                                             0.007                                                                            0.003                                                                            0.02                                                                             0.009                                                                            0.01                                                                             0.10                                                                             0.032                                                                            0.003                                                                            0.003                                                                            0.00008                                87 0.007                                                                            0.01                                                                             0.15                                                                             0.009                                                                            0.005                                                                            0.04                                                                             0.008                                                                            0.01                                                                             0.18                                                                             0.025                                                                            0.003                                                                            0.002                                                                            0.00011                          Compara-                                                                            88 0.007                                                                            0.01                                                                             0.12                                                                             0.010                                                                            0.002                                                                            0.03                                                                             0.005                                                                            0.01                                                                             0.03                                                                             0.021                                                                            0.003                                                                            0.003                                                                            0.00007                          tive  89 0.007                                                                            0.01                                                                             0.10                                                                             0.011                                                                            0.002                                                                            0.03                                                                             0.004                                                                            0.01                                                                             0.25                                                                             0.023                                                                            0.003                                                                            0.003                                                                            0.00008                                90 0.009                                                                            0.01                                                                             0.15                                                                             0.013                                                                            0.003                                                                            0.04                                                                             0.006                                                                            0.01                                                                             0.12                                                                             0.060                                                                            0.003                                                                            0.003                                                                            0.00005                          __________________________________________________________________________

                                      TABLE 18                                    __________________________________________________________________________             Heat-                                                                             Finish  Dehydrogenate                                                                         Anneal-                                                                            Normal-  Cavity  Tensile                                                                            Magnetic                       ing Rolling Heat treating                                                                         ing  izing                                                                              Thick-                                                                            Defect                                                                            Ferrite                                                                           Strength                                                                           Flux Density          Steel    Temp.                                                                             Temp.                                                                             Shape                                                                             Temp.   Temp.                                                                              Temp.                                                                              ness                                                                              Size                                                                              Grain                                                                             (kgf/                                                                              (at                                                                           80Λ/m)         No.      (°C.)                                                                      (°C.)                                                                      Ratio                                                                             (°C.)                                                                          (°C.)                                                                       (°C.)                                                                       (mm)                                                                              (μ)                                                                            No. mm.sup.2)                                                                          (tesla)               __________________________________________________________________________    Inven-                                                                              81 1150                                                                              940 0.9 700     --   --   100 25  -1  48.8 1.10                  tion  82 1150                                                                              940 0.9 700     --   --   100 20  -3  49.1 1.30                        83 1250                                                                              980 0.8 720     --   --   500 90  -1  51.3 0.90                        84 1250                                                                              980 0.8 720     850  --   500 90  -1  52.5 0.95                        85 1250                                                                              980 0.8 720     --   930  500 90  -1  46.3 0.92                        86 1250                                                                              920 1.1 --      850  --    40 10   0  48.8 1.00                        87 1250                                                                              910 1.2 --      --   930   20  5   0  58.8 0.95                  Compara-                                                                            88 1250                                                                              930  0.85                                                                             680     --   --   200 80   0  37.1 0.85                  tive  89 1250                                                                              930  0.85                                                                             680     --   --   200 80   0  62.1 0.45                        90 1250                                                                              930  0.85                                                                             680     --   --   200 80   5  51.3 0.50                  __________________________________________________________________________

We claim:
 1. A method of producing non-oriented magnetic steel heavyplate having high magnetic flux density comprising the stepsof:preparing a steel slab comprising, by weight, up to 0.01 percentcarbon, up to 0.20 percent manganese, up to 0.015 percent phosphorus, upto 0.010 percent sulfur, up to 0.05 percent chromium, up to 2.0 percentnickel, up to 0.01 percent molybdenum, up to 0.01 percent copper, up to0.004 percent nitrogen, up to 0.005 percent oxygen and up to 0.0002percent hydrogen, and one or more deoxidizing agents selected from agroup consisting of up to 4.0 percent silicon, up to 0.20 percenttitanium, 0.005 to 0.40 percent aluminum, and up to 0.01 percentcalcium, with the remainder being substantially iron; heating the slabto a temperature of 1150° to 1350° C.; carrying out at least onehot-rolling at a shape ratio A of at least 0.7 at a finish rollingtemperature of at least 900° C.; applying dehydrogenation heat treatmentat between 600° and 750° C. for heavy plate with a gage thickness of 50mm or more; annealing at a temperature of 700° to 950° C. or normalizingat a temperature of 910° to 1000° C., as required; annealing at atemperature of 750° to 950° C. or normalizing at a temperature of 910°to 1000° C. for hot-rolled heavy plate having a gage thickness that isat least 20 mm but less than 50 mm; whereby a magnetic flux density of0.8 tesla or more at a magnetic field of 80 A/m is imparted to thesteel;wherein the hot rolling is accomplished using a rolling rollhaving a radius R (mm) and wherein the steel heavy plate has anentry-side thickness h₁ (mm) and an exit-side plate thickness h₀ (mm)which exhibit a relationship with rolled shape ratio A of the hotrolling as follows: ##EQU3##
 2. The method according to claim 1 thatincludes the step of preparing a steel slab comprising, by weight, up to0.01 percent carbon, up to 0.02 percent silicon, up to 0.20 percentmanganese, up to 0.015 percent phosphorus, up to 0.010 percent sulfur,up to 0.05 percent chromium, up to 0.01 percent molybdenum, up to 0.01percent copper, 0.005 to 0.40 percent aluminum, up to 0.004 percentnitrogen, up to 0.005 percent oxygen and up to 0.0002 percent hydrogen,with the remainder being substantially iron.
 3. The method according toclaim 1 that includes the step of cold-rolling at a reduction ratio ofbetween 5 and 25 percent, prior to the annealing.
 4. The methodaccording to claim 1 that includes the steps of heating the slab to atemperature of 1200° to 1350° C. and hot-rolling with a finishingtemperature in the ferrite zone at or below the Ar₃ transformationpoint.
 5. The method according to claim 2 wherein the composition of thesteel contains 0.1 to 1.0 percent silicon and up to 0.005 percentaluminum.
 6. The method according to claim 2 wherein the composition ofthe steel contains 0.005 to 0.03 percent titanium and up to 0.005percent aluminum.
 7. The method according to claim 2 wherein thecomposition of the steel contains 0.0005 to 0.01 percent calcium and upto 0.005 percent aluminum.
 8. The method according to claim 2 whereinthe composition of the steel contains 0.005 to 0.03 percent titanium,0.0005 to 0.01 percent calcium and up to 0.005 percent aluminum.
 9. Themethod according to claim 2 wherein the composition of the steelcontains 1.0 to 4.0 percent silicon and up to 0.040 percent aluminum.10. The method according to claim 2 wherein the composition of the steelcontains 0.01 to 2.0 percent nickel.
 11. The method according to claim 2wherein the composition of the steel contains 0.04 to 0.20 percenttitanium and up to 0.040 percent aluminum.